Originally, the study of genetics concentrated on discrete genes that resulted in a few identifiable diseases. Mendel’s theory of inheritance was grounded on gene inheritance patterns, including autosomal dominant, autosomal recessive, autosomal trisomy, X-linked dominant, X-linked recessive disorders, and Y-chromosome linked disorders (Yule, 1907).
However, epidemiologic studies strongly suggested that there were nonidentified genes that were strongly associated with the development of a multitude of additional diseases and conditions. This quest led to the Human Genome Project. The Human Genome Project was conducted from 1990 to 2003 to map and sequence the entire human genome. The result has been the identification of over 1,800 genes associated with various diseases. According to Healthy People 2020, genomics plays a role in nine of the 10 leading causes of death, including heart disease, cancer, stroke, diabetes and Alzheimer’s disease. In addition, over 1,000 genetic tests were developed to facilitate diagnosis.
Genetic epidemiology focuses on the risk of developing disease, in populations that have a genetic basis, and is now recognized as a component of risk analysis. This chance of developing a disease, in the absence of other risk factors, gives credence to the potential of a genetic etiology. For example, what are the chances of a smoker developing lung cancer compared to a nonsmoker developing lung cancer? We know that not all smokers develop lung cancer and we also recognize that nonsmokers develop lung cancer. Therefore, a premise could involve a genetic predisposition or susceptibility. Or, is there yet another confounding variable? Through epidemiological studies, radon gas (an environmental factor) was found to be another cause of lung cancer. These types of etiological questions are being explored (along with conventional research studies) through new genetic technology. There are some chronic diseases that are associated with family history and genetic inheritance is thought to be a major contributing factor for some cancers, for diabetes, and for cardiovascular disease. The outcomes of these technological advances have implications in the clinical management of individuals and populations on the primary, secondary, or tertiary levels of prevention.
The explosion of new genetic information has had a profound impact on healthcare. It is essential for the advanced practice nurse (APN) to be able to integrate this new information to effect positive outcomes. In recognition of the added responsibilities, the following APN core competencies have been developed.
- Genetics– The study of individual genes and their impact on relatively rare single gene disorders (Consensus Panel on Genetic/Genomic Nursing Competencies, 2009)
- Genomics– The study of all genes in the human genome as well as their interaction with other genes, the individual’s environment, and the influence of cultural and psychosocial factors (Consensus Panel on Genetic/Genomic Nursing Competencies, 2009)
- Genetic epidemiology– The link of epidemiology and genetics (Khoury, Bety, & Cohen, 1993)
Conducting an accurate family history for three generations can reveal a wealth of information on which to base prevention strategies. If the information collected is used to counsel individuals on how to decrease risk with lifestyle modifications (before the patient has the disease) then the utilization of the family history would be considered a primary intervention. For example, if the family history identifies an increased risk for breast cancer, the patient is counseled to modify lifestyle choices to minimize risk. The information should also result in screening strategies that result in the early identification of the disease. The screening strategies would be considered secondary prevention strategies (Spector et al., 2009).
Consider the following pieces of information: (1) A history of malignant melanoma in a first-degree relative has been associated with an eightfold increase in risk (Glanz, Saraiya, Wechsler, 2002); (2) having a sister with a BRCA1 mutation gives a woman a 50% risk of having the same genetic mutation (Jacobellis et al., 2004); and (3) similarly, there is a nearly 9% chance or risk for children with relatives who have epilepsy to develop the disease (Epilepsy Foundation, n.d.).
As an APN, how do you translate this information to best inform a family faced with a life-altering decision?
As the APN discusses risk with his or her patients, it is important to reflect on the meaning of the various ways risk is expressed. Without a clear understanding of the terminology that describes risk, no meaningful discussion or decision making can take place. As noted under the core competencies, one of the roles the APN assumes is interpreting the risk for patients to ensure informed decision making. Although risk terminology has been discussed previously, certain aspects bear repeating.
- Absolute risk is the probability of an event, such as illness, injury, or death
- Absolute risk gives no indication of how its magnitude compares with others.
- The odds ratio closely approximates the relative risk if the disease is rare.
- Odds ratio and the relative risk are used to assess the strength of association between risk factor and outcome.
- Attributable risk is used to make risk-based decisions for individuals.
- Population-attributable risk measures are used to form public health decisions (Nordness, 2006).
In addition, the APN must consider the possibility that home testing, for a variety of genetic conditions, is available. Due to easy access on the Internet, patients may present the APN with results from home testing that they do not understand, and with no concept of the implications of validity and reliability (Wolfberg, 2006).
The APN has a responsibility in the role of genetic counselor to patients. Of course, the interdisciplinary aspect of providing optimal healthcare must also be considered. Referrals to a genetic counselor may be appropriate. However, the APN must be willing to carry out the competencies as described previously, such as informing the patient of the importance of accruing accurate, detailed information about their family history. In 2004, a survey indicated that 96% of people felt that family history was important to their health but less than 30% actually had relevant family history to share (Awareness of family health history as a risk factor for disease–United States, 2004). The healthcare provider must recognize that all aspects of elucidating, teaching, counseling, and supporting need to be done considering the patients’ cultural context. Cultural aspects can influence comprehension and interpretation of genetic testing, treatments, and implications (Hamilton & Bowers, 2007).
One of the additional responsibilities when possessing prescriptive authority is the necessity of having a thorough knowledge of pharmacogenomics. It has been acknowledged that the effect of medications has a range of therapeutic and nontherapeutic responses. Age, weight, ethnic background, and physiologic impairments associated with disease processes were often concomitant with these variations. Due to the recent genomic research, it is now acknowledged that genetic variations can affect mediation efficacy, toxicity, and drug interaction outside of the drugs themselves (National Institute of Health, 2009). Certainly the specifics and implications of these variations will be discussed, in detail, in pharmacology.